Locator: 48737SPP.
Map of North America's Regional Transmission Organizations (RTOs). Similar maps can easily be found. This is from Arcus Power Corp that suggests that some RTOs, such as Midcontinent Independent System Operator (MISO) and Southwest Power Pool (SPP) do not accurately represent the actual cost of energy and capacity.
Go to the link to see that discussion.
Here's the map, posted March 11, 2024:
What makes this interesting is this press release from SPP that was dated March 20, 2025:
From the link:
On June 4, 2024, SPP filed its amended tariff with FERC to accommodate requirements for Western entities pursuing RTO membership or increased participation as part of the expansion of the SPP RTO: Basin Electric Power Cooperative; Colorado Springs Utilities; Deseret Power Electric Cooperative; the Municipal Energy Agency of Nebraska (MEAN); Platte River Power Authority; Tri-State Generation and Transmission Association; and the Western Area Power Administration Colorado River Storage Project, Rocky Mountain and Upper Great Plains regions.
The expansion of the RTO is part of Aspire 2026, SPP’s five-year strategic plan, which details opportunities to fully integrate Western facilities into SPP’s existing market system in a way that creates meaningful, equitable value for new and existing members.
Again, these are the seven western entities, which are now part of the "eastern" SPP RSO:
Basin Electric Power Cooperative; Colorado Springs Utilities; Deseret Power Electric Cooperative; the Municipal Energy Agency of Nebraska (MEAN); Platte River Power Authority; Tri-State Generation and Transmission Association; and the Western Area Power Administration Colorado River Storage Project, Rocky Mountain and Upper Great Plains regions.
The SPP RSO now extends from the Canadian border right down the mid-section of America to the northern "border" of ERCOT (Texas).
The Midcontinent Independent System Operator, Inc., formerly named Midwest Independent Transmission System Operator, Inc. (MISO) is an Independent System Operator (ISO) and Regional Transmission Organization (RTO) established in 1998.
It provides open-access transmission service and monitors the high-voltage transmission system in the Midwestern United States, in Manitoba, Canada, and in a southern U.S. region that includes much of Arkansas, Mississippi, and Louisiana.
MISO also operates one of the world's largest real-time energy markets. The 15 states covered by MISO are: Arkansas, Illinois, Indiana, Iowa, Kentucky, Louisiana, Michigan, Minnesota, Mississippi, Missouri, Montana, North Dakota, South Dakota, Texas, and Wisconsin.
North Dakota: it appears MISO's coverage in North Dakota is fairly small geographically compared to SPP but appears to take in a larger part of the North Dakota population.
From wiki, SPP:
Southwest Power Pool and its member companies coordinate the flow of electricity across approximately 60,000 miles of high-voltage transmission lines spanning 14 states. The company is headquartered in Little Rock, Arkansas.
